This page describes a Tactical Tracking System for high altitude balloons &ndash; or any other object &ndash; based on the [http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System Automatic Position Reporting System] (APRS). The term ''Tactical Tracking'' here refers to real-time tracking and chasing, where the coordinates of the tracked object are received in real time and sent to a car navigation unit that is able to dynamically update the target coordinates.

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This page describes a Tactical Tracking System for high altitude balloons &ndash; or any other object &ndash; based on the [http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System Automatic Position Reporting System] (APRS). The term ''Tactical Tracking'' here refers to real-time tracking and chasing, where the coordinates of the tracked object are received in real time and sent to a navigation unit that is able to dynamically update the target coordinates.

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The tracking system is based on APRS. Therefore it has many years of heritage and can take advantage of an existing global APRS network. It does not require any R&D since all components are available off-the shelf and even complete turn-key solutions are available.

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The tracking system is based on APRS and has many years of heritage. When used on standard amateur radio [http://info.aprs.net/index.php/Frequencies APRS frequencies] it can take advantage of the existing global APRS network of [http://info.aprs.net/index.php/Digipeater digipeaters] and [http://info.aprs.net/index.php/IGate IGates], but it can also be used in point-to-point links on any suitable frequency including unlicensed bands.

In addition to position reporting, the system can also transmit telemetry read via analog and/or digital inputs.

In addition to position reporting, the system can also transmit telemetry read via analog and/or digital inputs.

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The page is intended to present a reliable tracking solution for those not already familiar with APRS. If you are already using APRS, you may find the information on this page trivial.

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# The transmitter placed on-board the balloon. It transmits GPS coordinates and other telemetry at regular intervals.

# The transmitter placed on-board the balloon. It transmits GPS coordinates and other telemetry at regular intervals.

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# The global APRS network that receives the APRS packets from the balloon via [http://en.wikipedia.org/wiki/Digipeater digipeaters] and publishes them on the global APRS network, see http://aprs.fi/

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# The global APRS network that receives the APRS packets from the balloon via [http://info.aprs.net/index.php/Digipeater digipeaters] and [http://info.aprs.net/index.php/IGate IGates] and publishes them on the Itnernet, see http://aprs.fi/ &ndash; this can be used to follow the balloon trajectory from anywhere over the Internet.

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# A mobile APRS receiver station that is used for real time tactical navigation in the field where no Internet is available. This station also receives the APRS packets directly from the balloon.

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# A mobile APRS receiver station that is used for real time tactical navigation in the field where no Internet is available. This station receives the APRS packets directly from the balloon.

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''Diagram''

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A functional diagram of the complete tracking system is shown below followed by a description of each functional block.

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[[Image:TTS-FunctionalOverview.png|600px]]

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== System Design ==

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; GPS Receiver

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: The GPS receiver tracks GPS satellites and calculates the position of the balloon in real time. It sends standard NMEA formatted data to the APRS packet encoder. Besides the obvious low mass and power requirements, it is very important that the GPS receiver works above the 18km limit.

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; APRS Encoder (TNC)

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: The APRS encoder takes the input digital data (position and telemetry) and converts it into 1200bps [http://en.wikipedia.org/wiki/Frequency-shift_keying#Audio_FSK AFSK] audio signal. In other words, this is where the conversion from digital data to analog signal takes place.

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== Transmitter ==

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; FM Transmitter

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: The FM transmitter converts the audio signal containing the 1200bps AFSK data to VHF or UHF radio signal.

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=== GPS Receiver ===

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; FM Receiver

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: The FM Receiver receives the VHF/UHF radio signals and converts it into audio signal that contains the 1200bps AFSK data.

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; APRS Decoder (TNC)

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: The APRS decoder decodes the received AFSK data into APRS packets from where the balloon position and telemetry can be extracted. Technically, this is where the conversion from analog signal to digital data occurs.

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; Tactical Navigator

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: Car navigation unit that supports tactical navigation (chasing). It receives balloon position data from the TNC and plots it on the map. In tactical mode it updates the route from the current location to the target location (balloon position) in real time.

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; Telemetry Logger

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: This functional unit is used to log the received APRS packets from the balloon, both position report and telemetry packets. This can be a simple laptop or netbook connected to the TNC.

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; Digipeaters and IGates

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: These are automatically part of the system if using amateur radio [http://info.aprs.net/index.php/Frequencies APRS frequencies]. This is an existing infrastructure and will not be described further here.

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== Components ==

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This section presents the physical components of the tracking system and provides a mapping for each component to the functions they provide.

The GPS 18x LVC is a small, highly accurate GPS sensor featuring a 12-parallel-channel, WAAS-enabled GPS receiver and an integrated magnetic base. The receiver is 2.4 inches in diameter and weighs just 115 grams (depending on cable length), and it can operate at extremely high altitudes.

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The unit defaults to output data in the industry standard NMEA 0183 data format, but may also be user programmed to output data in the GARMIN proprietary format. It also provides a pulse-per-second logic level output whose rising edge is aligned to the UTC second within 1 microsecond.

The OpenTracker+ is an open source APRS tracker that receives NMEA data from a GPS receiver, encodes it into APRS packets and generates AFSK signal suitable for audio input to an FM transmitter. It can also transmit telemetry data that is read from the built-in temperature sensor (non-SMT version) as well as the available ADC channels.

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OpenTracker+ can be purchased assembled and tested or as a kit. Additionally, there is an SMT version, which is the one we are using. The SMT version does not include a built-in temperature sensor or LEDs.

The MX146 is an embeddable VHF transmitter module from SRB Electronics. It's programmable for any frequency from 144-148 MHz in 2.5 kHz steps, or it can be used on one of 16 pre-programmed frequencies.

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=== FM Transmitter ===

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The MX146 comes in two versions:

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* +8VDC version that gives > 500mW RF out

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* +5VDC version that gives > 350mW RF out

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== The Mobile Receiver Station ==

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We chose the 5V version because its lower power consumption and to allow operation of all components from a single 5VDC supply. In addition to the lower power consumption, the 5V version is capable of higher duty cycle than the 8V version.

The AvMap G5 is a personal navigator with vuilt-in 20-channel GPS receiver. What distinguishes the AvMap G5 from other personal navigators is that it has special firmware that supports APRS and it can be interfaced to the [[#Kenwood TM-D710E|Kenwood TM-D710E]] (or other APRS TNCs). Thus the G5 + TM-D710 provide the desired tactical navigation functions out of the box without any hacking!

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The built in APRS functionality allows the AvMap G5 to receive APRS data from the TM-D710 and plot it on the map using the APRS symbols. In tactical mode, the AvMap G5 can ''navigate to'' the position of an APRS station even if the station is moving, see video below.

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At the same time, the AvMap G5 can send GPS data to the TM-D710, which then can use this to report it's own location via APRS. In practice this means that those following the event via the web, e.g. http://aprs.fi/ can follow both the balloon and the chasing car at the same time. ''(TBC since I don't yet have the TM-D710 so I don't know if this is actually possible)''

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{|

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| {{#ev:youtube|IPH4mwn4uko}}

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|[[Image:G5.jpg|400px]]

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|}

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Resources:

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* Website: http://www.geosat.us/ or http://www.avmap.it/

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* [http://www.geosat.us/AvMapG5QST.pdf QST Review]

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* AvMap G5 videos on YouTube: http://www.youtube.com/user/w6gps#p/u

=== Telemetry Recorder ===

=== Telemetry Recorder ===

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Not yet decided... This will most likely be a lightweight laptop or netbook that can connect to the TM-D710 and record the received packets. Also TBC if this is at all necessary &ndash; maybe the AvMap G5 can perform this function.

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== Electrical Wiring ==

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''To be written...''

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== Money Budget ==

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=== On-board APRS Transmitter ===

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The prices for the on-board units have been derived from US $ assuming a 1:1 $-to-€ conversion ratio, which would be the case in Denmark (import tax + 25% VAT). This is probably the worst case in Europe.

Although the mobile tracking station consisting of the [[#Kenwood TM-D710E|TM-D710E]] radio and [[#AvMap G5|AvMap G5]] navigator is rather expensive, it is important to emphasize that they have many other uses than APRS tracking. Obviously, the [[#AvMap G5|AvMap G5]] can be used as standard car navigator, while the [[#Kenwood TM-D710E|TM-D710E]] can be used for standard VHF/UHF amateur radio operations, including satellite communications. So this setup is very feasible if dual-use can be exploited.

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If this is not the case, cheaper alternatives can be considered consisting of a simple VHF FM receiver and 1200 bps TNC + laptop. One could even ditch the hardware modem and use soundcard modem, though this could be unreliable under difficult and weak signal conditions. This could be improved by switching to 300 bps operating mode.

Latest revision as of 21:05, 2 June 2010

This page describes a Tactical Tracking System for high altitude balloons – or any other object – based on the Automatic Position Reporting System (APRS). The term Tactical Tracking here refers to real-time tracking and chasing, where the coordinates of the tracked object are received in real time and sent to a navigation unit that is able to dynamically update the target coordinates.

The tracking system is based on APRS and has many years of heritage. When used on standard amateur radio APRS frequencies it can take advantage of the existing global APRS network of digipeaters and IGates, but it can also be used in point-to-point links on any suitable frequency including unlicensed bands.

In addition to position reporting, the system can also transmit telemetry read via analog and/or digital inputs.

The page is intended to present a reliable tracking solution for those not already familiar with APRS. If you are already using APRS, you may find the information on this page trivial.

Functional Overview

The tracking system consists of the following subsystems:

The transmitter placed on-board the balloon. It transmits GPS coordinates and other telemetry at regular intervals.

The global APRS network that receives the APRS packets from the balloon via digipeaters and IGates and publishes them on the Itnernet, see http://aprs.fi/ – this can be used to follow the balloon trajectory from anywhere over the Internet.

A mobile APRS receiver station that is used for real time tactical navigation in the field where no Internet is available. This station receives the APRS packets directly from the balloon.

A functional diagram of the complete tracking system is shown below followed by a description of each functional block.

GPS Receiver

The GPS receiver tracks GPS satellites and calculates the position of the balloon in real time. It sends standard NMEA formatted data to the APRS packet encoder. Besides the obvious low mass and power requirements, it is very important that the GPS receiver works above the 18km limit.

APRS Encoder (TNC)

The APRS encoder takes the input digital data (position and telemetry) and converts it into 1200bps AFSK audio signal. In other words, this is where the conversion from digital data to analog signal takes place.

FM Transmitter

The FM transmitter converts the audio signal containing the 1200bps AFSK data to VHF or UHF radio signal.

FM Receiver

The FM Receiver receives the VHF/UHF radio signals and converts it into audio signal that contains the 1200bps AFSK data.

APRS Decoder (TNC)

The APRS decoder decodes the received AFSK data into APRS packets from where the balloon position and telemetry can be extracted. Technically, this is where the conversion from analog signal to digital data occurs.

Tactical Navigator

Car navigation unit that supports tactical navigation (chasing). It receives balloon position data from the TNC and plots it on the map. In tactical mode it updates the route from the current location to the target location (balloon position) in real time.

Telemetry Logger

This functional unit is used to log the received APRS packets from the balloon, both position report and telemetry packets. This can be a simple laptop or netbook connected to the TNC.

Digipeaters and IGates

These are automatically part of the system if using amateur radio APRS frequencies. This is an existing infrastructure and will not be described further here.

Components

This section presents the physical components of the tracking system and provides a mapping for each component to the functions they provide.

Garmin GPS 18x LVC

The GPS 18x LVC is a small, highly accurate GPS sensor featuring a 12-parallel-channel, WAAS-enabled GPS receiver and an integrated magnetic base. The receiver is 2.4 inches in diameter and weighs just 115 grams (depending on cable length), and it can operate at extremely high altitudes.

The unit defaults to output data in the industry standard NMEA 0183 data format, but may also be user programmed to output data in the GARMIN proprietary format. It also provides a pulse-per-second logic level output whose rising edge is aligned to the UTC second within 1 microsecond.

OpenTracker+ SMT

The OpenTracker+ is an open source APRS tracker that receives NMEA data from a GPS receiver, encodes it into APRS packets and generates AFSK signal suitable for audio input to an FM transmitter. It can also transmit telemetry data that is read from the built-in temperature sensor (non-SMT version) as well as the available ADC channels.

OpenTracker+ can be purchased assembled and tested or as a kit. Additionally, there is an SMT version, which is the one we are using. The SMT version does not include a built-in temperature sensor or LEDs.

SRB MX146LV

The MX146 is an embeddable VHF transmitter module from SRB Electronics. It's programmable for any frequency from 144-148 MHz in 2.5 kHz steps, or it can be used on one of 16 pre-programmed frequencies.

The MX146 comes in two versions:

+8VDC version that gives > 500mW RF out

+5VDC version that gives > 350mW RF out

We chose the 5V version because its lower power consumption and to allow operation of all components from a single 5VDC supply. In addition to the lower power consumption, the 5V version is capable of higher duty cycle than the 8V version.

Kenwood TM-D710E

The Kenwood TM-D710E is a VHF/UHF transceiver featuring a dual receiver (receive to frequencies at the same time), built in packet TNC and APRS support.

The APRS support is extremely well suited for tactical tracking when combined with the AvMap G5 navigation unit.

The TM-D710E can perform the following functions in balloon tracking (some are TBC):

Direct reception of APRS packets from the balloon

Send received balloon position to the AvMap G5 tactical navigator (or other unit that supports the Kenwood format)

Digipeat received balloon packets

Get own location from AvMap G5 GPS (or other compatible GPS receiver)

Send own location via APRS network.

With the optional VGS-1 voice unit installed the TM-D710E can even read out loud the received APRS packets.

Specifications

Receiver

118-524 and 800-1300 MHz

Transmitter

2m and 70cm amateur bands

TX power

5 / 10 / 50W

Modes

F1D, F2D, F3E

Voltage

13.8 V DC ±15%

RX Current

< 1.2A at 2W audio out

TX Current

5.0 / 6.5 / 13.0A

Operating temperature

-20°C to +60°C

Weight

1.2 + 0.3 kg

AvMap G5

The AvMap G5 is a personal navigator with vuilt-in 20-channel GPS receiver. What distinguishes the AvMap G5 from other personal navigators is that it has special firmware that supports APRS and it can be interfaced to the Kenwood TM-D710E (or other APRS TNCs). Thus the G5 + TM-D710 provide the desired tactical navigation functions out of the box without any hacking!

The built in APRS functionality allows the AvMap G5 to receive APRS data from the TM-D710 and plot it on the map using the APRS symbols. In tactical mode, the AvMap G5 can navigate to the position of an APRS station even if the station is moving, see video below.

At the same time, the AvMap G5 can send GPS data to the TM-D710, which then can use this to report it's own location via APRS. In practice this means that those following the event via the web, e.g. http://aprs.fi/ can follow both the balloon and the chasing car at the same time. (TBC since I don't yet have the TM-D710 so I don't know if this is actually possible)

Telemetry Recorder

Not yet decided... This will most likely be a lightweight laptop or netbook that can connect to the TM-D710 and record the received packets. Also TBC if this is at all necessary – maybe the AvMap G5 can perform this function.

Electrical Wiring

To be written...

Money Budget

On-board APRS Transmitter

The prices for the on-board units have been derived from US $ assuming a 1:1 $-to-€ conversion ratio, which would be the case in Denmark (import tax + 25% VAT). This is probably the worst case in Europe.

Mobile Tracking Station

Although the mobile tracking station consisting of the TM-D710E radio and AvMap G5 navigator is rather expensive, it is important to emphasize that they have many other uses than APRS tracking. Obviously, the AvMap G5 can be used as standard car navigator, while the TM-D710E can be used for standard VHF/UHF amateur radio operations, including satellite communications. So this setup is very feasible if dual-use can be exploited.

If this is not the case, cheaper alternatives can be considered consisting of a simple VHF FM receiver and 1200 bps TNC + laptop. One could even ditch the hardware modem and use soundcard modem, though this could be unreliable under difficult and weak signal conditions. This could be improved by switching to 300 bps operating mode.